'\"
'\" Generated from file 'transmitter\&.man' by tcllib/doctools with format 'nroff'
'\" Copyright (c) 2006-2009 Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>
'\"
.TH "transfer::transmitter" n 0\&.2 tcllib "Data transfer facilities"
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.BS
.SH NAME
transfer::transmitter \- Data source
.SH SYNOPSIS
package require \fBTcl  8\&.4\fR
.sp
package require \fBsnit  ?1\&.0?\fR
.sp
package require \fBtransfer::copy  ?0\&.2?\fR
.sp
package require \fBtransfer::data::source  ?0\&.2?\fR
.sp
package require \fBtransfer::connect  ?0\&.2?\fR
.sp
package require \fBtransfer::transmitter  ?0\&.2?\fR
.sp
\fBtransfer::transmitter\fR \fIobjectName\fR ?\fIoptions\fR\&.\&.\&.?
.sp
\fBtransfer::transmitter\fR \fBstream channel\fR \fIchan\fR \fIhost\fR \fIport\fR ?\fIarg\fR\&.\&.\&.?
.sp
\fBtransfer::transmitter\fR \fBstream file\fR \fIpath\fR \fIhost\fR \fIport\fR ?\fIarg\fR\&.\&.\&.?
.sp
\fIobjectName\fR \fBmethod\fR ?\fIarg arg \&.\&.\&.\fR?
.sp
\fIobjectName\fR \fBdestroy\fR
.sp
\fIobjectName\fR \fBstart\fR
.sp
\fIobjectName\fR \fBbusy\fR
.sp
.BE
.SH DESCRIPTION
.PP
This package pulls data sources and connection setup together into a
combined object for the transmission of information over a socket\&.
These objects understand all the options from objects created
by the packages \fBtransfer::data::source\fR and
\fBtransfer::connect\fR\&.
.SH API
.SS "PACKAGE COMMANDS"
.TP
\fBtransfer::transmitter\fR \fIobjectName\fR ?\fIoptions\fR\&.\&.\&.?
This command creates a new transmitter object with an associated Tcl
command whose name is \fIobjectName\fR\&.
This \fIobject\fR command is explained in full detail in the sections
\fBObject command\fR and \fBObject methods\fR\&. The set of
supported \fIoptions\fR is explained in section \fBOptions\fR\&.
.sp
The object command will be created under the current namespace if the
\fIobjectName\fR is not fully qualified, and in the specified
namespace otherwise\&.
The fully qualified name of the object command is returned as the
result of the command\&.
.TP
\fBtransfer::transmitter\fR \fBstream channel\fR \fIchan\fR \fIhost\fR \fIport\fR ?\fIarg\fR\&.\&.\&.?
This method creates a fire-and-forget transfer for the data contained
in the channel \fIchan\fR, starting at the current seek location\&. The
channel is configured to use binary translation and encoding for the
transfer\&.
The channel is automatically closed when the transfer has completed\&.
.sp
If both \fIhost\fR and \fIport\fR are provided an \fBactive\fR
connection to the destination is made\&. If only a \fIport\fR is
specified (with \fIhost\fR the empty string) then a \fBpassive\fR
connection is made instead\&.
.sp
Any arguments after the port are treated as options and are used to
configure the internal transmitter object\&.
See the section \fBOptions\fR for a list of the supported options
and their meaning\&.
\fINote\fR however that the signature of the command prefix specified
for the \fB-command\fR callback differs from the signature for the
same option of the transmitter object\&.
This callback is only given the number of bytes and transfered, and
possibly an error message\&. No reference to the internally used
transmitter object is made\&.
.sp
The result returned by the command is the empty string
if it was set to make an \fIactive\fR connection, and the port the
internal transmitter object is listening on otherwise, i\&.e when it is
configured to connect \fIpassive\fRly\&.
See also the package \fBtransfer::connect\fR and the description
of the method \fBconnect\fR for where this behaviour comes from\&.
.TP
\fBtransfer::transmitter\fR \fBstream file\fR \fIpath\fR \fIhost\fR \fIport\fR ?\fIarg\fR\&.\&.\&.?
This method is like \fBstream channel\fR, except that the data
contained in the file \fIpath\fR is transfered\&.
.PP
.SS "OBJECT COMMAND"
All objects created by the \fB::transfer::transmitter\fR command have
the following general form:
.TP
\fIobjectName\fR \fBmethod\fR ?\fIarg arg \&.\&.\&.\fR?
The method \fBmethod\fR and its \fIarg\fR'uments determine the
exact behavior of the command\&.
See section \fBObject methods\fR for the detailed
specifications\&.
.PP
.SS "OBJECT METHODS"
.TP
\fIobjectName\fR \fBdestroy\fR
This method destroys the object\&. Doing so while a transmission is in
progress will cause errors later on, when the transmission completes
and tries to access the now missing data structures of the destroyed
object\&.
.TP
\fIobjectName\fR \fBstart\fR
This method initiates the data transmission, setting up the connection
first and then copying the information\&.
The method will throw an error if a transmission is already/still in
progress\&.
I\&.e\&. it is not possible to run two transmissions in parallel on a
single object, only in sequence\&. Multiple transmitter objects are
needed to manage parallel transfers, one per transmission\&.
Errors will also be thrown if the configuration of the data source is
invalid, or if no completion callback was specified\&.
.sp
The result returned by the method is the empty string
for an object configured to make an \fIactive\fR connection, and the port the
object is listening on otherwise, i\&.e when it is
configured to connect \fIpassive\fRly\&.
See also the package \fBtransfer::connect\fR and the description
of the method \fBconnect\fR for where this behaviour comes from\&.
.TP
\fIobjectName\fR \fBbusy\fR
This method returns a boolean value telling us whether a transmission
is in progress (\fBTrue\fR), or not (\fBFalse\fR)\&.
.PP
.SS OPTIONS
All transmitter objects support the union of the options supported
by their connect and data source components, plus two of their own\&.
See also the documentation for the packages
\fBtransfer::data::source\fR and \fBtransfer::connect\fR\&.
.TP
\fB-blocksize\fR \fIint\fR
This option specifies the size of the chunks to be transmitted in one
block\&. Usage is optional, its default value is \fB1024\fR\&.
.TP
\fB-command\fR \fIcmdprefix\fR
This option specifies the command to invoke when the transmission of
the information has been completed\&.
The arguments given to this command are the same as given to the
completion callback of the command \fBtransfer::copy::do\fR provided
by the package \fBtransfer::copy\fR\&.
.TP
\fB-mode\fR \fImode\fR
This option specifies the mode the object is in\&. It is optional and
defaults to \fBactive\fR mode\&. The two possible modes are:
.RS
.TP
\fBactive\fR
In this mode the two options \fB-host\fR and \fB-port\fR are
relevant and specify the host and TCP port the object has to connect
to\&. The host is given by either name or IP address\&.
.TP
\fBpassive\fR
In this mode the option \fB-host\fR has no relevance and is ignored
should it be configured\&.
The only option the object needs is \fB-port\fR, and it specifies
the TCP port on which the listening socket is opened to await the
connection from the partner\&.
.RE
.TP
\fB-host\fR \fIhostname-or-ipaddr\fR
This option specifies the host to connect to in \fIactive\fR mode,
either by name or ip-address\&. An object configured for \fIpassive\fR
mode ignores this option\&.
.TP
\fB-port\fR \fIint\fR
For \fIactive\fR mode this option specifies the port the object is
expected to connect to\&. For \fIpassive\fR mode however it is the port
where the object creates the listening socket waiting for a
connection\&. It defaults to \fB0\fR, which allows the OS to choose
the actual port to listen on\&.
.TP
\fB-socketcmd\fR \fIcommand\fR
This option allows the user to specify which command to use to open a
socket\&. The default is to use the builtin \fB::socket\fR\&. Any
compatible with that command is allowed\&.
.sp
The envisioned main use is the specfication of \fBtls::socket\fR\&. I\&.e\&.
this option allows the creation of secure transfer channels, without
making this package explicitly dependent on the \fBtls\fR package\&.
.sp
See also section \fBSecure connections\fR\&.
.TP
\fB-encoding\fR encodingname
.TP
\fB-eofchar\fR eofspec
.TP
\fB-translation\fR transspec
These options are the same as are recognized by the builtin command
\fBfconfigure\fR\&. They provide the configuration to be set for the
channel between the two partners after it has been established, but
before the callback is invoked (See method \fBconnect\fR)\&.
.TP
\fB-string\fR \fItext\fR
This option specifies that the source of the data is an immediate
string, and its associated argument contains the string in question\&.
.TP
\fB-channel\fR \fIhandle\fR
This option specifies that the source of the data is a channel, and
its associated argument is the handle of the channel containing the
data\&.
.TP
\fB-file\fR \fIpath\fR
This option specifies that the source of the data is a file, and its
associated argument is the path of the file containing the data\&.
.TP
\fB-variable\fR \fIvarname\fR
This option specifies that the source of the data is a string stored
in a variable, and its associated argument contains the name of the
variable in question\&. The variable is assumed to be global or
namespaced, anchored at the global namespace\&.
.TP
\fB-size\fR \fIint\fR
This option specifies the size of the data transfer\&. It is optional
and defaults to -1\&. This value, and any other value less than zero
signals to transfer all the data from the source\&.
.TP
\fB-progress\fR \fIcommand\fR
This option, if specified, defines a command to be invoked for each
chunk of bytes transmitted, allowing the user to monitor the progress
of the transmission of the data\&. The callback is always invoked with
one additional argument, the number of bytes transmitted so far\&.
.PP
.SH "SECURE CONNECTIONS"
One way to secure connections made by objects of this package is to
require the package \fBtls\fR and then configure the option
\fB-socketcmd\fR to force the use of command \fBtls::socket\fR to
open the socket\&.
.CS


    # Load and initialize tls
    package require tls
    tls::init -cafile /path/to/ca/cert -keyfile \&.\&.\&.

    # Create a connector with secure socket setup,
    transfer::transmitter T -socketcmd tls::socket \&.\&.\&.
    \&.\&.\&.

.CE
.SH "TLS SECURITY CONSIDERATIONS"
.PP
This package uses the \fBTLS\fR package to handle the
security for \fBhttps\fR urls and other socket connections\&.
.PP
Policy decisions like the set of protocols to support and what
ciphers to use are not the responsibility of \fBTLS\fR, nor of
this package itself however\&.
Such decisions are the responsibility of whichever application is
using the package, and are likely influenced by the set of servers
the application will talk to as well\&.
.PP
For example, in light of the recent
\fIPOODLE attack\fR [http://googleonlinesecurity\&.blogspot\&.co\&.uk/2014/10/this-poodle-bites-exploiting-ssl-30\&.html] discovered by Google many servers will disable support
for the SSLv3 protocol\&.
To handle this change the applications using \fBTLS\fR must be
patched, and not this package, nor \fBTLS\fR itself\&.
Such a patch may be as simple as generally activating \fBtls1\fR
support, as shown in the example below\&.
.CS


    package require tls
    tls::init -tls1 1 ;# forcibly activate support for the TLS1 protocol

    \&.\&.\&. your own application code \&.\&.\&.

.CE
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems\&.
Please report such in the category \fItransfer\fR of the
\fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&.
Please also report any ideas for enhancements you may have for either
package and/or documentation\&.
.PP
When proposing code changes, please provide \fIunified diffs\fR,
i\&.e the output of \fBdiff -u\fR\&.
.PP
Note further that \fIattachments\fR are strongly preferred over
inlined patches\&. Attachments can be made by going to the \fBEdit\fR
form of the ticket immediately after its creation, and then using the
left-most button in the secondary navigation bar\&.
.SH KEYWORDS
channel, copy, data source, secure, ssl, tls, transfer, transmitter
.SH CATEGORY
Transfer module
.SH COPYRIGHT
.nf
Copyright (c) 2006-2009 Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>

.fi
